Exercise 2.  Observe that the subroutine NewtonSystem involves vector functions and is not dependent on the dimension.
Use the subroutine NewtonSystem to solve the nonlinear system in 3D space:  

        [Graphics:Images/BroydenMethodMod_gr_41.gif]   
        [Graphics:Images/BroydenMethodMod_gr_42.gif]  
        [Graphics:Images/BroydenMethodMod_gr_43.gif]  
    
Hint.  There are four solutions.  Good starting vectors are  [Graphics:Images/BroydenMethodMod_gr_44.gif].  

Solution 2.

First, enter the coordinate functions [Graphics:../Images/BroydenMethodMod_gr_45.gif] and construct the vector function  [Graphics:../Images/BroydenMethodMod_gr_46.gif]  using Mathematica, and then find the Jacobian matrix [Graphics:../Images/BroydenMethodMod_gr_47.gif].  

[Graphics:../Images/BroydenMethodMod_gr_48.gif]


[Graphics:../Images/BroydenMethodMod_gr_49.gif]

Second, graph the surfaces  [Graphics:../Images/BroydenMethodMod_gr_50.gif],  [Graphics:../Images/BroydenMethodMod_gr_51.gif]  and  [Graphics:../Images/BroydenMethodMod_gr_52.gif]  using Mathematica.  The points of intersection are the solutions we seek.  

[Graphics:../Images/BroydenMethodMod_gr_53.gif]


[Graphics:../Images/BroydenMethodMod_gr_54.gif]

[Graphics:../Images/BroydenMethodMod_gr_55.gif]

(i)  Use the Newton-Raphson method to find a numerical approximation to the solution near  [Graphics:../Images/BroydenMethodMod_gr_56.gif].  

[Graphics:../Images/BroydenMethodMod_gr_57.gif]


[Graphics:../Images/BroydenMethodMod_gr_58.gif]

(ii)  Use the Newton-Raphson method to find a numerical approximation to the solution near  [Graphics:../Images/BroydenMethodMod_gr_59.gif].  

[Graphics:../Images/BroydenMethodMod_gr_60.gif]


[Graphics:../Images/BroydenMethodMod_gr_61.gif]

(iii)  Use the Newton-Raphson method to find a numerical approximation to the solution near  [Graphics:../Images/BroydenMethodMod_gr_62.gif].  

[Graphics:../Images/BroydenMethodMod_gr_63.gif]


[Graphics:../Images/BroydenMethodMod_gr_64.gif]

(iv)  Use the Newton-Raphson method to find a numerical approximation to the solution near  [Graphics:../Images/BroydenMethodMod_gr_65.gif].  

[Graphics:../Images/BroydenMethodMod_gr_66.gif]


[Graphics:../Images/BroydenMethodMod_gr_67.gif]

We are done.

Aside.  We can have Mathematica solve the system analytically.  There is a surprise.

[Graphics:../Images/BroydenMethodMod_gr_68.gif]


[Graphics:../Images/BroydenMethodMod_gr_69.gif]

 

 

[Graphics:../Images/BroydenMethodMod_gr_70.gif]

 

Since Mathematica performs its solution using complex number arithmetic, the first four solutions are extraneous.
The solutions that we seek are the latter four solutions where x, y, and z are real numbers.  

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(c) John H. Mathews 2005